JP2016176873A - Method for manufacturing coaxial metal body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a coaxial metal body, which uses a metal stacking 3D printer and enables the manufacture of a coaxial structure where a core wire is in the center of outer metal at any portion, while being electrically floating.SOLUTION: There is provided a method for manufacturing a coaxial metal body including: tube shaped outer metal 11; and inner metal 12 disposed inside the outer metal 11. A 3D printer forms: the outer metal 11 having a discontinuous portion 14 and apertures 16; the inner metal 12 having facing portions that face the respective apertures 16; and a connecting metal member 20 for temporarily supporting the inner metal 12 relative to the outer metal 11 at the discontinuous portion 14. Insulating members 40 are inserted from the apertures 16, and the insulating members 40 are disposed between the apertures 16 and the facing portions so as to support the inner metal 12 relative to the outer metal 11. The connecting metal member 20 is subsequently removed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for manufacturing a coaxial metal body using a metal laminated 3D printer.

  A shielded loop antenna often used as a near-field probe is expected to have only a magnetic field sensitivity and no sensitivity to an electric field due to a shield structure. Patent Document 1 discloses a magnetic field probe that is configured by a coaxial line in which a dielectric member is disposed between a core wire and an outer conductor. In addition, as a method of manufacturing a shielded loop antenna, there are a method of manufacturing by using a coaxial cable by hand processing and a method of manufacturing using a printed board manufacturing technique (photolithography technique).

  However, in the method of manufacturing a sealed dead loop antenna by using a coaxial cable and manually processing, it is difficult to obtain the accuracy required for the sealed dead loop antenna. In addition, in the method of manufacturing a shielded loop antenna using printed circuit board manufacturing technology, the electrical length becomes longer due to the influence of the substrate material such as glass epoxy, and the upper limit of the transmission / reception frequency of the antenna is lowered. It was. Furthermore, when a shielded loop antenna is manufactured using a coaxial cable or a semi-rigid cable, the sensitivity of the electric field may occur due to the asymmetry of the structure.

  On the other hand, for a method of manufacturing an electronic and / or mechanical structure, component, and apparatus used in the electronics industry or the like using a 3D printer using a metal laminated 3D printing technology, for example, Patent Document 2 Is disclosed. That is, Patent Document 2 proposes a method of manufacturing a coaxial structure by metallization treatment of a dielectric.

JP 2014-85167 A Special table 2014-527474 gazette

  In the manufacturing method of the coaxial structure by the metallization process of the dielectric material in patent document 2, it is possible to manufacture the metal which floated in the hollow. However, in a curved structure such as a shielded loop antenna, it is sometimes impossible to manufacture a coaxial structure having a core wire at the center from any part of the outer metal in an electrically floating state.

  The object of the present invention is to manufacture a coaxial structure in which the core wire is centered from the outer genus of any part even in a curved structure such as a shielded loop antenna, using a metal laminated 3D printing technology. It is providing the manufacturing method of the coaxial metal body which can do.

  A method for manufacturing a coaxial metal body according to one aspect of the present invention is a method for manufacturing a coaxial metal body including a tube-shaped outer metal and an inner metal disposed inside the outer metal, and includes a discontinuous portion and an opening. An outer metal having an inner metal having an opposing portion facing the opening, and a connecting metal member that temporarily supports the inner metal with respect to the outer metal at the discontinuous portion are formed using a 3D printer, and the insulating member is formed from the opening. And inserting an insulating member between the opening and the facing portion so as to support the inner metal with respect to the outer metal, and removing the connecting metal member.

  According to the present invention, it is possible to manufacture a coaxial structure in which the core wire is centered from the outer genus of any part in an electrically floating state, even if the coaxial metal body is an accurate and curved structure. .

FIG. 6 is a diagram (1) for explaining a basic operation of a 3D printer using a metal laminated 3D printing technique. It is FIG. (2) for demonstrating the basic operation | movement of the 3D printer using a metal lamination | stacking 3D printing technique. FIG. 10 is a diagram (3) for explaining the basic operation of the 3D printer using the metal lamination 3D printing technology. (A) is a figure for demonstrating the process of inserting the insulating member 40 in the sealed dead loop antenna 10 manufactured with the metal lamination | stacking 3D printer, (b) is a figure of the sealed dead loop antenna shown to (a). It is a side view which shows the structure of one edge part. (A) is a partially enlarged perspective view showing an enlarged portion A of the sealed dead loop antenna shown in FIG. 4 (a), and (b) is a discontinuous portion of the outer metal of the sealed dead loop antenna shown in (a). It is the side view which looked at from the arrow C direction. It is a figure for demonstrating the process for main-fixing the inner side metal 12 to the outer side metal 11. FIG. It is a figure for demonstrating the other process for main-fixing the inner side metal 12 to the outer side metal 11. FIG. It is a figure for demonstrating the case where the arrangement | positioning number of the through-hole 16 provided in the predetermined location of the outer side metal 11 is changed. It is a figure for demonstrating the other process for main-fixing the inner side metal 12 to the outer side metal 11. FIG. It is a graph by the TDR simulation which shows the improvement condition of the high frequency characteristic (characteristic impedance) by the presence or absence of the recessed part 17. FIG. It is a graph by the simulation of TDR which shows the improvement condition of the high frequency characteristic (characteristic impedance) by the presence or absence of the recessed part 17 and the recessed part 18. FIG. It is a figure which shows the other example of the recessed part formed in the inner side metal 12 and / or the outer side metal 11. FIG. It is a figure which shows the shielded loop antenna 50 of another shape.

  Hereinafter, a method for manufacturing a coaxial metal body according to one aspect of the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

  When a shielded loop antenna is manufactured by a 3D printer using a metal laminated 3D printing technique, an extremely symmetrical structure can be manufactured. For example, in a 3D printer that uses metal lamination 3D printing technology, further improvement can be expected due to technological progress. However, in the current technology, metal powder is laminated in steps of 0.05 mm, so about ± 0.025 mm. Accuracy is ensured. For this reason, if the center conductor has a coaxial structure with a diameter of about 1 mm, the tolerance is about ± 2.5%. That is, in the 3D printer using the metal lamination 3D printing technique, a modeled object can be manufactured with an accuracy of 0.05 mm. Therefore, a modeled object having a total length of 10 cm can be manufactured with an accuracy of 0.05%.

  On the other hand, when the semi-rigid cable is bent manually, the accuracy is limited to about ± 1 mm. In the printed board manufacturing technology, the accuracy of characteristic impedance affected by errors such as the thickness of the insulator and the pattern width is about ± 10%. In addition, the printed board has a problem of warping of the substrate. For example, a printed board having a dimension of 30 mm or less has a warpage of the substrate of about 1% with respect to the entire length. As described above, by using a 3D printer using the metal laminated 3D printing technology, a shielded loop antenna can be manufactured with high accuracy.

  1, 2 and 3 are diagrams for explaining the basic operation of the 3D printer using the metal lamination 3D printing technology. 2 and 3, the shielded loop antenna 10 described later is taken as an example, but it can also be used for other methods of manufacturing a coaxial metal body.

  Fig.1 (a) is a perspective view which shows the process in which the metal powder of the 1st layer is sprinkled by the recoater on the modeling table of 3D printer. The metal powder M is supplied to the recoater 2 by a supply device (not shown). The recoater 2 moves above the modeling table 1 with a slight gap, and the first layer having a uniform thickness is formed on the modeling table 1. A metal powder layer M1 is formed. This state is also shown in FIG. As shown in FIG. 2A, the modeling table 1 is configured to move up and down inside the modeling tank 5 by the lifting device 4, and when the first metal powder layer M1 is formed by the recoater 2. The upper surface of the modeling table 1 coincides with the upper end 5F of the modeling tank 5.

  In FIG. 1B, the metal powder layer M1 formed on the modeling table 1 by the process of FIG. 1A is irradiated with the laser light L from the laser light source 3 so that the metal powder M is melted and the metal MT. Shows the process. This state is also shown in FIG. As shown in FIG. 2 (b), the laser light L from the laser light source 3 is irradiated only on the portion of the metal powder layer M1 that is desired to be the metal MT.

  FIG. 2 (c) shows a process in which the second metal powder layer M2 is laminated by the recoater 2 on the first metal powder layer M1 shown in FIG. 2 (b). . After the first metal powder layer M1 is laminated by the recoater 2 and the irradiation of the laser light L by the laser light source 3 is finished, the modeling table 1 is moved to the first metal powder layer M1 by the lifting device 4. Decrease by thickness. Therefore, when the recoater 2 forms the second metal powder layer M2, the upper surface of the first metal powder layer M1 coincides with the upper end 5F of the modeling tank 5.

  FIG. 2D shows a process in which the laser light L 3 irradiates the second metal powder layer M2 laminated on the modeling table 1 by the process of FIG. 2C. It is. Similarly to the metal powder layer M1, the laser light L from the laser light source 3 is applied only to the portion of the metal powder layer M2 that is to be the metal MT. After the laser light source 3 finishes irradiating the metal powder layer M2 with the laser light L, the elevating device 4 lowers the modeling table 1 by the thickness of the second metal powder layer M2, and thereafter the metal powder layer M2 is similarly metal. Formation of the powder layer and irradiation with the laser beam L are performed.

  FIG.2 (e) is sectional drawing which shows the state by which the metal powder layer was laminated | stacked over multiple layers on the modeling table in a modeling tank. When the recoater 2 forms the Kth metal powder layer MK, as shown in FIG. 2 (e), the upper surface of the K-1th metal powder layer M (K-1) is formed on the modeling tank. 5 is made to coincide with the upper end 5F.

  FIG. 2 (f) shows a state in which the metal powder layer is laminated on the modeling table in the modeling tank up to the final layer, and the sealed dead loop antenna 10 including the core wire and the outer metal is formed in the metal powder layer. It is sectional drawing shown.

  FIG. 3A is a transparent perspective view of an example of a sealed dead loop antenna formed inside a metal powder layer laminated to the last layer on a modeling table. Actually, the modeling table 1 on which the metal powder layers M1 to MN are laminated can be removed from the modeling tank 5 as shown in FIG. 3A, and the metal powder that is not the metal MT is removed. The shielded loop antenna 10 can be taken out. The sealed dead-loop antenna 10 taken out from the modeling table 1 has a hollow structure and has an inner metal 12 inside the outer metal 11 as described later.

  FIG.3 (b) is a perspective view which shows the process of taking out the sealed dead loop antenna shown to Fig.3 (a) from a metal powder layer, and removing the metal powder clogged in. Since the metal powder still remains in the hollow portion of the sealed dead loop antenna 10 taken out from the modeling table 1, the internal metal powder M is removed as shown in FIG. Thus, after the step of removing the internal metal powder M, the sealed dead loop antenna 10 in which the inner metal 12 is formed inside the outer metal 11 can be made.

  FIG. 4A is a diagram for explaining a process of inserting the insulating member 40 through the shielded loop antenna 10 manufactured by the metal laminated 3D printer. FIG. 4B is a side view showing the structure of one end of the shielded loop antenna shown in FIG.

  As shown in FIG. 4A, the shielded loop antenna 10 manufactured by the metal laminated 3D printer includes an outer metal 11 and an inner metal 12. The inner metal 12 is coaxial with the outer metal 11, and there is a space 13 between the outer metal 11 and the inner metal 12. The shielded loop antenna 10 includes a loop-shaped portion 10L and straight portions 10S formed at both ends of the loop-shaped portion 10L. An end portion of the straight portion 10 </ b> S is open, and the inner metal 12 protrudes from the end portion 15.

  In order to temporarily hold the inner metal 12 inside the outer metal 11, the loop-shaped portion 10 </ b> L of the shielded loop antenna 10 has a discontinuous portion 14, and the discontinuous portion 14 first supports the inner metal 12 temporarily. The connecting metal member 20 is provided. A second connecting metal member 30 that temporarily supports the inner metal 12 protruding from the end 15 so as to be centered (coaxial) with respect to the outer metal 11 at the end 15 of the straight portion 10S of the shielded loop antenna 10. Is provided.

  An insulating member 40 for permanently fixing the inner metal 12 so as to be coaxial with the outer metal 11 is inserted into the loop-shaped portion 10L of the sealed dead-loop antenna 10, or a molten resin not shown in the drawing. A through-hole 16 is provided as an opening for injecting. The step of permanently fixing the inner metal 12 so as to be coaxial with the outer metal 11 using the insulating member 40 or molten resin will be described later.

  As shown in FIG. 4B, the second connection metal member 30 includes two legs 31 and 32 and two arms 33 and 34. The two legs 31 and 32 are attached so that their base portions are opposed to the outer peripheral portion of the outer metal 11 of the straight portion 10S of the shielded loop antenna 10, and are extended in parallel to the inner metal 12. The ends of the two legs 31 and 32 are connected to one ends of arms 33 and 34 that are orthogonal to the legs 31 and 32 and face the inner metal 12. The other ends of the two arms 33 and 34 are connected to the end of the inner metal 12 and temporarily hold the inner metal 12 so that the inner metal 12 is coaxial with the outer metal 11.

  A thin portion 35 is provided in the vicinity of the attachment portion of the two legs 32, 32 to the outer metal 11, and the thickness of the two legs 31, 32 at this portion is thin. Similarly, a thin portion 35 is also provided in the vicinity of the connection portion between the two arms 33 and 34 with the inner metal 12, and the thickness of the two arms 33 and 34 in this portion is reduced. For this reason, after the inner metal 12 is held on the outer metal 11 by a method described later, the second connecting metal member 30 can be easily formed by cutting the second connecting metal member 30 at the position of the thin portion 35. Can be removed.

  5A is an enlarged perspective view of the discontinuous portion 14, and FIG. 5B is a view of the discontinuous portion 14 shown in FIG.

  As shown in FIGS. 5A and 5B, the discontinuous portion 14 is discontinuous with only the outer metal 11 cut out by a predetermined length, and the inner metal 12 is continuous. The first connecting metal member 20 provided in the discontinuous portion 14 includes two long rods 21 and 22 that connect the discontinuous portion 14 in parallel to the inner metal 12, and a central portion of the long rods 21 and 22. Are respectively provided with short rods 23 and 24 for connecting to the inner metal 12.

  The two long rods 21, 22 are connected to the discontinuous portion 14 at a position facing each other with the inner metal 12 interposed therebetween, and the two long rods 21, 22 are thin on the portion close to the outer metal 11. A portion 25 is provided, and the thickness of the two long rods 21 and 22 in this portion is thin. The portions of the short rods 23 and 24 that connect the central portions of the long rods 21 and 22 to the inner metal 12 are connected to the inner metal 12, respectively. For this reason, after the inner metal 12 is held on the outer metal 11 by the method described later, the first connecting metal member 20 is cut at the position of the thin portion 25 and the position of the small diameter portion 26 to obtain the first One connecting metal member 20 can be easily removed.

  FIG. 6 is a diagram for explaining a process for permanently fixing the inner metal 12 to the outer metal 11.

  In order to remove the first connecting metal member 20 and the second connecting metal member 30 from between the outer metal 11 and the inner metal 12 manufactured using the 3D printer, the inner metal 12 is permanently fixed to the outer metal 11. There is a need to. Therefore, the insulating member 40 is inserted into the plurality of through holes 16 provided in the loop-shaped portion 10 </ b> L of the outer metal 11 shown in FIG. 4A to fix the inner metal 12 to the outer metal 11.

  FIG. 6A is a cross-sectional view of part B of the shielded loop antenna 10 shown in FIG. The insulating member 40 is a resin-made columnar member, and the tip portion has a dome shape. On the other hand, a concave portion 17 for adjusting the high frequency characteristics of the inner metal (coaxial metal body) 12 is formed on the outer peripheral surface of the inner metal 12 facing the through hole 16 into which the insulating member 40 is inserted. The recess 17 is formed in a spherical shape that matches the dome shape at the tip of the insulating member 40. Three through-holes 16 are provided on the circumference of the same position of the outer metal 11, and all three insulating members 40 have the same shape.

  FIG. 6B is a cross-sectional view showing a state in which the resin columnar member shown in FIG. 6A is inserted through a through hole provided in the outer metal and supports the inner metal. When the insulating member 40 is inserted into each of the three through holes 16, the dome-shaped tip is inserted into the recess 17, and the rear end of the insulating member 40 is fixed to the through hole 16, the state shown in FIG. By fixing the three insulating members 40 in this way, the inner metal 12 is fixed coaxially inside the outer metal 11.

  FIG. 6C shows a modification of the resin insulating member 40 through which the through hole 16 provided in the outer metal 11 is inserted. The insulating member 40 ′ of the modified example is also a resin columnar member, and the tip portion has a dome shape, but includes a stopper 43 having a tapered inclined surface 41 and a step surface 42 on the side surface of the columnar portion.

  FIG. 6D is a cross-sectional view showing a state in which the inner metal is supported by the outer metal by the insulating member 40 ′ of the modified example shown in FIG. As shown in FIG. 6D, the insulating member 40 ′ having the stopper 43 is inserted into the through hole 16, and the stepped surface 42 is passed through the through hole 16 so that the step surface 42 is the inner peripheral surface of the outer metal 11. The inner metal 12 is fixed coaxially inside the outer metal 11.

  As shown in FIG. 6B or FIG. 6D, the discontinuous portion 14 is formed as described with reference to FIG. 5 after the process for permanently fixing the inner metal 12 to the outer metal 11 is completed. The first connecting metal member 20 is cut off at the end, the second connecting metal member 30 is cut off at the end, and the manufacturing process of the shielded loop antenna 10 is completed.

  In the shielded loop antenna 10, the shape of the outer metal 11 is not limited to the shape shown in FIG. 4A, and may be other shapes (for example, see FIG. 13). In the shielded loop antenna 10, the arrangement positions of the through holes 16 that permanently fix the inner metal 12 to the outer metal 11 are not limited to four as shown in FIG. The number may be 5 or more. In the shielded loop antenna 10, the disposition portion of the discontinuous portion 14 is not limited to one place as shown in FIG. 4A, and may be two or more places. In FIG. 6, three insulating members are inserted and the inner metal 12 is finally fixed to the outer metal 11. However, two or less or four or more insulating members are inserted and the inner metal 12 is permanently fixed to the outer metal 11. You may do it.

  FIG. 7 is a diagram for explaining another process for permanently fixing the inner metal 12 to the outer metal 11.

  In the shielded loop antenna 10 shown in FIGS. 4 and 6, the inner metal 12 is permanently fixed to the outer metal 11 by inserting the insulating member 40 from the through hole 16 provided in the outer metal 11. In contrast, the inner metal 12 is permanently fixed to the outer metal 11 by injecting molten resin (hereinafter simply referred to as “molten resin”) from the through-hole 16 provided in the outer metal 11 and curing the resin. You may do it.

  Fig.7 (a) is explanatory drawing which shows the process of inject | pouring molten resin from the through-hole provided in the outer metal of the shielded loop antenna shown to Fig.4 (a). As shown in FIG. 7A, nozzles 44 are inserted into the plurality of through holes 16 provided in the loop-shaped portion 10 </ b> L of the outer metal 11, and the molten resin is supplied from the molten resin supply source 45 between the outer metal 11 and the inner metal 12. Inject and fill the space 13.

  FIG. 7B is a partially cutaway view showing a state in which the inner metal located at the portion facing the through hole provided in the outer metal of the sealed dead loop antenna shown in FIG. It is a fragmentary perspective view. As shown in FIG. 7B, the outer peripheral surface of the facing portion of the inner metal 12 facing the through hole 16 provided in the outer metal 11 is for adjusting the high frequency characteristics of the inner metal (coaxial metal body) 12. The recess 17 is formed. The cross-sectional shape of the recess 17 provided on the outer peripheral surface of the inner metal 12 is a curved surface. In the shielded loop antenna 10 shown in FIG. 4, when the other process shown in FIG. 7A is adopted, it is preferable to form the recess 17 of the inner metal 12 as shown in FIG. 7B. .

  FIG.7 (c) is a fragmentary sectional view which shows the process with which resin is filled into the inside of an outer metal from the through-hole shown to (b). When the molten resin is injected from the through hole 16, the molten resin is filled in the space 13 between the outer metal 11 and the inner metal 12 as shown in FIG. FIG. 7C shows a state in which the molten resin injected from one through hole 16 is gradually filled into the space 13 between the outer metal 11 and the inner metal 12.

  The molten resin is injected in a sufficient amount until it wraps around the inner metal 12 so that the inner metal 12 is disposed inside the outer metal 11. The ripple-shaped curve indicates that the molten resin injected from one through hole 16 gradually spreads in the space 13 over time. When the molten resin filled in the space 13 is cooled and solidified, the inner metal 12 is fixed coaxially inside the outer metal 11.

  When the molten resin is filled into the space 13 between the outer metal 11 and the inner metal 12 from the through hole 16 provided in the outer metal 11 and the resin cools and hardens, the inner metal 12 is fixed in the outer metal 11 in a coaxial state. The Therefore, when the inner metal 12 is permanently fixed to the outer metal 11 using a molten resin, three through holes 16 are not necessarily required as shown in FIG.

  FIG. 8 is a diagram for explaining a case where the number of through holes 16 provided in a predetermined location of the outer metal 11 is changed.

  FIG. 8A shows an embodiment in which the number of through holes 16 provided at a predetermined location of the outer metal 11 is one. FIG. 8B shows an embodiment in which the number of through holes 16 provided at a predetermined location of the outer metal 11 is two. FIG. 8 (c) shows an embodiment in which the number of through holes 16 provided at a predetermined location of the outer metal 11 is four. As shown in FIGS. 8A to 8C, the number of through holes provided in the outer metal of the shielded loop antenna is not limited to three as shown in FIG. 4A. 8A to 8C, a concave portion 17 having a curved surface for adjusting high frequency characteristics is formed on the outer peripheral surface of the inner metal 12 facing the through hole 16. Has been. As shown in FIG. 6, the same applies to the case where the inner metal 12 is permanently fixed to the outer metal 11 using the insulating member 40.

  FIG. 9 is a view for explaining still another process for permanently fixing the inner metal 12 to the outer metal 11.

  In another method for fixing the inner metal 12 to the outer metal 11 as shown in FIG. 7A, molten resin is injected from the three through holes 16 and the concave portion having the curved surface shown in FIG. 17 was provided on the inner metal 12. On the other hand, in yet another process shown in FIG. 9, molten resin is injected from the four through holes 16 to further deform the inner shapes of the inner metal 12 and the outer metal 11.

  FIG. 9 (a) shows that through holes provided at predetermined locations on the outer metal are in opposing positions, and a stepped diameter expansion portion is formed on the inner peripheral surface of the outer metal, and a stepped diameter reduction portion is formed on the outer peripheral surface of the corresponding inner metal. It is a fragmentary sectional view which shows the state with which resin was filled between the outer side metal and the inner side metal provided. As shown in FIG. 9A, in addition to the recess 17 provided on the outer peripheral surface of the inner metal 12, a recess 18 is also provided on the inner peripheral surface of the outer metal 11. The concave portion 17 provided on the outer peripheral surface of the inner metal 12 facing the through hole 16 is provided by reducing the diameter of the inner metal 12, and the degree of the reduced diameter is the largest at the portion facing the through hole 16. The greater the distance from the 16 opposing parts, the smaller the degree of diameter reduction. The diameter reduction of the inner metal 12 is not limited to a stepped one as shown in FIG. 9A, and can be performed continuously.

  As shown in FIG. 9A, the inner peripheral surface of the outer metal 11 in the peripheral part of the through hole 16 is expanded in diameter to be provided with a recess 18. The degree of diameter expansion of the recess 18 is the largest in the through hole 16 and the peripheral part, and the degree of diameter expansion is smaller as the distance from the through hole 16 is larger. The diameter reduction of the outer metal 11 is not limited to a stepwise adjustment according to the diameter reduction of the recess 17 as shown in FIG. 9A, and can be performed continuously. When the shielded loop antenna 10 shown in FIG. 4 employs another process shown in FIG. 9, the concave portion 17 of the inner metal 12 and the concave portion 18 of the outer metal 11 are formed as shown in FIG. It is preferable to form.

  In FIG. 9B, molten resin is injected from four through holes 16 provided at predetermined positions of the outer metal 11, and the molten resin gradually fills the space 13 between the outer metal 11 and the inner metal 12. The state of being done is shown. The ripple-like curve shown in FIG. 9B shows how the resin gradually spreads in the space 13 when the molten resin is simultaneously injected from the four through holes 16. . When the molten resin filled in the space 13 is cooled and solidified, the inner metal 12 is fixed coaxially inside the outer metal 11.

  Below, the effect | action of the recessed part 17 formed in the outer peripheral surface of the inner side metal 12 and the recessed part 18 formed in the inner peripheral surface of the outer side metal 11 is demonstrated. The concave portion 17 and the concave portion 18 have high-frequency characteristics by matching the characteristic impedance calculated from the dielectric constant and space occupancy of the resin filling the space 13 with the design value of the coaxial structure including the outer metal 11 and the inner metal 12. It is the structure for suppressing the deterioration of.

First, the recessed part 17 shown to Fig.6 (a) is demonstrated. The value (b / a) obtained by dividing the diameter of the inner metal 12 by a, the inner diameter of the outer metal 11 by b, and the inner diameter b of the outer metal 11 by the diameter a of the inner metal 12 is k. The diameter of the insulating member 40 is v, the number is n, and the relative dielectric constant is εs. The equivalent relative dielectric constant εr in the case where the inner metal 12 shown in FIG.
εr = (s0 + ss (εs-1)) / s0 (1)
Here, s0 is the cross-sectional area of the space 13 (= π (b ² + a ² )), and ss is the cross-sectional area of the insulating member 40 (= v (b−a) n).
Then, the ratio k = b / a can be calculated by the following formula 2.
k = 10 ^{[(50 × √εr) / 138]} (2)

Under the condition of equivalent dielectric constant εr, the ratio of k2 = b / a is calculated from Equation 2.
From this k 2, the depth δ of the concave portion 17 is determined by the following Equation 3.
δ = [a ² × (1- [k ² / k ^{2 2} ]) × π] / 3v (3)
Here, k is the ratio of b / a of the coaxial structure obtained by Equation 2, k2 is the b / a2 ratio when the influence of the insulating member 40 is considered, and a2 is the equivalent central conductor radius considering the influence of the insulating member 40 It is.

As a calculation example, for example, when a = 1 and εr = 1, k = 2.3 is determined using Equation 2.
Next, when the relative dielectric constant εs of the insulating member 40 is 2.0, the diameter of the insulating member 40 is v = 0.5 mm, and the number of the insulating members 40 is 3 as shown in FIG.
From Equation 1, εr = 1.44, and from Equation 3, δ = 0.23 mm.
Here, k = 2.3 and k2 = 2.44 are calculated using Equation 2.

  FIG. 10 is a graph by TDR simulation showing how the high-frequency characteristics (characteristic impedance) are improved by the presence or absence of the recesses 17.

  FIG. 10A is a graph showing the high-frequency characteristics when there is no annular recess on the outer peripheral surface of the inner metal facing the through hole provided in the outer metal. FIG.10 (b) is a graph which shows a high frequency characteristic when there exists an annular recessed part in the outer peripheral surface of the inner side metal facing the through-hole provided in the outer side metal (state shown in FIG.6 (b)). 10A and 10B, the vertical axis represents characteristic impedance (500 mW corresponds to 50Ω), and the horizontal axis represents horizontal distance (0.1 ns corresponds to 7 mm).

  In FIG. 10A, a depressed waveform appears in the vicinity of 0.2 ns, whereas in FIG. 10B, a depressed waveform as seen in FIG. 10A does not appear. That is, it can be seen that the characteristic impedance is stable by providing the recess 17 in the inner metal 12.

Next, the recessed part 17 and the recessed part 18 shown to Fig.9 (a) are demonstrated. As shown in FIG. 9A, the concave portion 17 and the concave portion 18 have a three-step step structure. That is, between the inner metal 12 and the outer metal 11, there is an A region where only air is present, a B region where resin and air are mixed, and a C region where resin is filled. In the structure shown in FIG. 9A, the characteristic impedance Z ₀ representing the high frequency characteristics of the coaxial structure in the three regions A, B, and C is all made to coincide with each other by the following expression 4 to suppress deterioration of the high frequency characteristics. Is.
Z ₀ = (138 / √εn) log (b / a) (4)

As a specific calculation example, the procedure for making all the characteristic impedances in the three regions A, B, and C coincide with 50Ω is as follows.
(1) The dimensions of the coaxial structure are such that the diameter of the inner metal 12 is a and the inner diameter of the outer metal 11 is b.
(2) The relative dielectric constant of the fixing resin is εs.
(3) The dimensions of the area A are as basic.
(4) Equivalent relative dielectric constant εr = εs / 2 in region B.
(5) For the size of the coaxial structure in the region B, the ratio of k = b / a obtained by Equation 2 is calculated.
(6) The dimension in the region B is determined so that b / a becomes k.
(7) Equivalent relative dielectric constant εr = εs in region C.
(8) The ratio k is obtained using Equation 2.
(9) The dimension in the region C is determined so that b / a becomes k.

In addition, the dimension of the level | step difference d of the recessed part 17 in a three-step step structure can be made as small as possible using the following Formula 5.
d = (− b + ak) / (1 + k) (5)
For example, when a = 1.5, b = 3.4, and k = 4.2, d = 0.56, and the new a2 and b2 are as follows.
a2 = ad = 0.94
b2 = b + d = 3.96

  FIG. 11 is a graph by TDR simulation showing how the high frequency characteristics (characteristic impedance) are improved depending on the presence or absence of the recess 17 and the recess 18.

  FIG. 11A shows a case where there is no annular recess 17 on the outer peripheral surface of the inner metal 12 facing the through hole 16 provided in the outer metal 11 and there is no annular recess 18 on the inner peripheral surface of the outer metal 11. It is a graph which shows a high frequency characteristic. In FIG. 11B, an annular recess 17 is provided on the outer peripheral surface of the inner metal 12 facing the through hole 16 provided in the outer metal 11, and an annular recess 18 on the inner peripheral surface of the outer metal 11 is provided. It is a graph which shows the high frequency characteristic in the case of. 11A and 11B, the vertical axis represents characteristic impedance (500 mW corresponds to 50Ω), and the horizontal axis represents horizontal distance (0.1 ns corresponds to 7 mm).

  In FIG. 11 (a), a waveform that is depressed in a plurality of stages appears in the vicinity of 0.1 to 0.3 ns, whereas in FIG. 11 (b), a depression as seen in FIG. 11 (a). No waveform appears. That is, it can be seen that the characteristic impedance is stable by providing the recess 17 in the inner metal 12 and the recess 18 in the outer metal 11.

  FIG. 12 is a diagram illustrating another example of the recess formed in the inner metal 12 and / or the outer metal 11.

  FIG. 12A shows an example in which the recess 18 is provided only around the through hole 16 provided in the outer metal 11. FIG. 12B shows another embodiment in which the recess 18 is provided only around the through hole 16 provided in the outer metal 11. FIG. 12C is an example in which the periphery of the through-hole 16 provided in the outer metal 11 is flat, and the step-shaped recess 17 is provided only in the portion facing the through-hole 16 of the inner metal 12. In the shielded loop antenna 10 shown in FIG. 4 (a), it is possible to adopt the shape of the recess formed in the inner metal 12 and / or the outer metal 11 as shown in FIGS. 12 (a) to 12 (c). it can. In addition, the shape of the recessed parts 17 and 18 is not limited to these shapes.

  FIG. 13 is a diagram illustrating a 3D shielded loop antenna 50 having another shape. 13A is a plan view of the 3D sealed dead-loop antenna 50, and FIG. 13B is a side view of the 3D sealed dead-loop antenna 50 shown in FIG. 13A.

  A 3D shielded loop antenna 50 shown in FIG. 13 is an antenna for measuring a magnetic field in a three-dimensional direction, and can be manufactured by a coaxial metal body manufacturing method similar to that of the shielded loop antenna 10 described above. Specifically, the outer metal 11 is formed by the first connecting metal connecting member provided at the discontinuous portion and the second connecting metal connecting member provided at the end portion by the 3D printer using the metal laminated 3D printing technology. On the other hand, the outer skeleton of the 3D sealed dead loop antenna 50 in which the inner metal 12 is temporarily held is formed. Thereafter, the inner metal 12 is permanently fixed to the outer metal by inserting an insulating member through a through hole (not shown), and the first connecting metal connecting member and the second connecting metal connecting member are separated. The production of the dead loop antenna 50 is finished.

  The 3D sealed dead loop antenna 50 is formed by combining three sealed dead loop antennas 51, 52, and 53. The three shielded loop antennas 51, 52, 53 are combined radially at intervals of 120 degrees, and the loop-shaped portions 51L, 52L, 53L are bent about 35 degrees with respect to the straight portions 51S, 52S, 53S. The 3D shielded loop antenna 50 can measure magnetic fields in the X direction, the Y direction, and the Z direction with one antenna element. Thus, according to the manufacturing method of the coaxial metal body of the present application, various types of shielded loop antennas can be manufactured.

DESCRIPTION OF SYMBOLS 10 Sealed loop antenna 10L Loop-like part 10S Linear part 11 Outer metal 12 Inner metal 14 Discontinuous part 16 Through-hole (opening part)
17, 18 Concave 20 First connecting metal member 21, 22 Long rod 23, 24 Short rod 30 Second connecting metal member 31, 32 Leg 33, 34 Arm 40 Insulating member 50 3D sealed dead loop antenna

Claims (8)

A method for producing a coaxial metal body comprising a tubular outer metal and an inner metal disposed inside the outer metal,
The outer metal having a discontinuous portion and an opening, the inner metal having a facing portion facing the opening, and a connecting metal member that temporarily supports the inner metal with respect to the outer metal at the discontinuous portion. Formed using a 3D printer,
An insulating member is inserted from the opening, and the insulating member is disposed between the opening and the facing portion so as to support the inner metal with respect to the outer metal.
Removing the connecting metal member;
The manufacturing method of the coaxial metal body characterized by having a process.   A recess for adjusting high-frequency characteristics of the coaxial metal body is formed in at least one of a peripheral portion of the opening and the facing portion when the insulating member is disposed. Item 2. A method for producing a coaxial metal body according to Item 1.   The concave portion is provided only in the facing portion, the concave portion has a curved surface, and the distal end portion into which the insulating member is inserted from the opening portion toward the concave portion is a dome-shaped columnar member, The method for manufacturing a coaxial metal body according to claim 2, wherein the tip portion is inserted into the recess.   The concave portion provided in the facing portion is provided by reducing the diameter of the inner metal, and the degree of the diameter reduction is the largest at the portion facing the opening, and the distance of the opening from the facing portion is large. 3. The method for producing a coaxial metal body according to claim 2, wherein the larger the size, the smaller the diameter reduction.   The concave portion provided in the peripheral portion of the opening is provided by expanding the inner diameter of the outer metal, and the degree of diameter expansion is the largest in the vicinity of the opening and the distance from the opening is large. The method for producing a coaxial metal body according to claim 2, wherein the degree of diameter expansion is small.   6. The coaxial metal body according to claim 4, wherein the diameter of the concave portion provided in the facing portion and the diameter of the concave portion provided in the peripheral portion of the opening are increased in stages. Production method.   The method for manufacturing a coaxial metal body according to any one of claims 4 to 6, wherein the insulating member is a molten resin, and is solidified after pouring from the opening.   8. The coaxial metal body according to claim 1, wherein the coaxial metal body has a loop antenna shape having an annular portion at a tip of a straight portion, and the inner metal protrudes from both end portions of the outer metal. The manufacturing method of the coaxial metal body as described in any one of.

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